Thrombus removal system and process

ABSTRACT

A device capable of capturing and facilitating the removal of a thrombus in blood vessels (or stones in biliary or urinary ducts, or foreign bodies) uses a soft coil mesh with the aid of a pull wire or string to engage the surface of a thrombus, and remove the captured thrombus. The soft coil mesh is formed by an elongated microcoil element that forms the helical elements of a macrocoil element. The microcoil element provides a relatively elastic effect to the helical elements forming the macrocoil and allows for control of gripping forces on the thrombus while reducing non-rigid contact of the device with arterial walls. The use of multiple coil mesh elements, delivered through a single lumen or multiple lumens, preferably with separate control of at least one end of each coil, provides a firm grasp on a distal side of a thrombus, assisting in non-disruptive or minimally disrupted removal of the thrombus upon withdrawal of the device.

RELATED APPLICATION DATA

The present application is a continuation of U.S. patent applicationSer. No. 11/356,321, filed Feb. 16, 2006, now U.S. Pat. No. 7,955,345,which is a continuation-in-part of U.S. patent application Ser. No.11/097,354, filed Apr. 1, 2005, now U.S. Pat. No. 7,955,344.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to intravascular medical devices. Moreparticularly, the present invention pertains to devices for isolating,capturing, and removing blood clots from a blood vessel. This samesystem may also be used to safely and effectively remove material fromother cavities of the body, such as, for example, foreign bodies, orstones from the urinary or the biliary tracts.

2. Background of the Art

The present invention pertains generally to thrombus collection andremoval. The process of thrombosis may produce a clot in a patient'svasculature. Such clots may occasionally be harmlessly dissolved in theblood stream. At other times, however, such clots may lodge in a bloodvessel or embolize to a distal blood vessel where they can partially orcompletely occlude the flow of blood. If the partially or completelyoccluded vessel provides blood to sensitive tissue such as the brain orheart, for example, serious tissue damage may result.

When symptoms of vascular occlusion are apparent, such as an occlusionresulting in a stroke, immediate intervention is required to minimizetissue damage. One approach is to treat a patient with clot dissolvingdrugs, such as recombinant tissue plasminogen activator, streptokinase,or heparin. These drugs, however, do not immediately dissolve the bloodclot and generally are useful only when administered within a short timeperiod after onset of stroke symptoms.

Published U.S. Patent Application 2005/0038447 describes A medicaldevice for removing clots from a blood vessel, comprising: a firstlongitudinally-oriented spine having a distal end; a pushing membercoupled to the proximal end of the first longitudinally-oriented spineand extending proximally therefrom; and a clot-grabbing basket generallydisposed between and coupled to the first longitudinally-oriented spine.

Published U.S. Patent Application 2004/0138692 discloses an embolusextractor, comprising: an elongated shaft having a proximal end and adistal end; first and second struts, each strut having a proximal endand a distal end coupled to the distal end of the shaft; the first andsecond struts having a first position and a second position, wherein inthe first position, the distal ends and the proximal ends of the strutsare spaced at a first distance, and in the second position the distalends and the proximal ends of the struts are spaced at a seconddistance, the second distance being less than the first distance; andthird and fourth struts, each strut coupled to one of the first andsecond struts via a proximal end and distal end.

Published U.S. Patent Application 2004/0098023 discloses a vasoocclusivedevice, comprising: a core member; and a fibrous structure carried bythe core member, the fibrous structure comprises one or more strands ofnanofibers. The vasoocclusive device may provide the fibrous structurein a product generated at least in part by an electrospinning processcomprises the steps of: supplying a polymer solution through a needle;electrostatically charging the needle; electrostatically charging ametal plate that is placed at a distance from the needle, the metalplate having a charge that is opposite that of the needle, therebysending a jet of the polymer solution towards the metal plate; andcollecting the fibrous structure from the metal plate.

Published U.S. Patent Application 2004/0039435 discloses aself-expanding, pseudo-braided device embodying a high expansion ratioand flexibility as well as conformability and improved radial force. Thepseudo-braided device is particularly suited for advancement through anddeployment within highly tortuous and very distal vasculature. Variousforms of the pseudo-braided device are adapted for the repair ofaneurysms and stenoses as well as for use in thrombectomies and embolicprotection therapy.

There are a variety of ways of discharging shaped coils and linear coilsinto a body cavity. In addition to those patents that describephysically pushing a coil out of the catheter into the body cavity(e.g., Ritchart et al.), there are a number of other ways to release thecoil at a specifically chosen time and site. U.S. Pat. No. 5,354,295 andits parent, U.S. Pat. No. 5,122,136, both to Guglielmi et al., describean electrolytically detachable embolic device.

A variety of mechanically detachable devices are also known. Variousexamples of these devices are described in U.S. Pat. No. 5,234,437, toSepetka, U.S. Pat. No. 5,250,071 to Palermo, U.S. Pat. No. 5,261,916, toEngelson, U.S. Pat. No. 5,304,195, to Twyford et al., U.S. Pat. No.5,312,415, to Palermo, and U.S. Pat. No. 5,350,397, to Palermo et al.

Various configurations have been used to remove calculi from the biliaryor urinary system. See, for instance, U.S. Pat. No. 5,064,428.Additionally, devices having various configurations have been used toremove objects from the vasculature. For example, surgical devicescomprising one or more expandable and collapsible baskets have beendescribed for removing or piercing a thrombus in the vasculature. See,U.S. Pat. Nos. 6,066,149. 5,868,754 describes a three prong-shapeddevice for capturing and removing bodies or articles from within avessel.

U.S. Pat. Nos. 5,895,398 and 6,436,112 to Wensel disclose a clot andforeign body removal device comprising a clot capture coil connected toan insertion mandrel within a catheter. The clot capture coil disclosedby Wensel is made out of a material with shape memory which allows it tobe deformed within the catheter and then reformed to its original coilconfiguration when the coil is moved outside of the catheter lumen. TheWeasel invention also provides for a biphasic coil which changes shapeupon heating or passing an electric current, wherein the coil can beused to ensnare and corkscrew a clot in a vessel, which is thenextracted from the vessel by moving the clot capture coil and catheterproximally until the clot can be removed. According to the Wenselinvention, foreign bodies are similarly captured by deploying the coildistal to the foreign body and moving the clot capture coil proximallyuntil the foreign body is trapped within the coil

Published U.S. Patent Application 2004/0225229 describes a devicecomprising a core wire having a distal end and a proximal end; acatheter shaft having a proximal catheter end, a distal catheter end anda lumen through which the core wire is passed such that the distal endof the core wire extends beyond the distal catheter end; a retrievalelement disposed at the distal end of the core wire, the retrievalelement movable from a radially contracted position to a radiallyexpanded position; and a first stop element attached to the core wire,the first stop element configured to prevent over-expansion of theretrieval element.

Among commercial thrombus-removal systems are at least the following:

-   -   1) The MERCI system of Concentric Medical that has a form of a        corkscrew or helix spring. In this system, which may use a large        0.018 F microcatheter, the microcatheter tip is first positioned        across the thrombus with the help of a guidewire after which the        guidewire is exchanged with the system which is deployed distal        and into the thrombus. The corkscrew shape of the device        facilitates penetration into the thrombus. The thrombus can then        be retrieved from the artery into a large 9 French guiding        catheter, and removed from the patient's body.    -   2) The In-Time system of Boston Scientific resembles a        clam-shell when compressed, but once the microcatheter is placed        through the thrombus and the device extended out of the        microcatheter, it expands into 4 strings that form an oval, as        with a rugby football. The system is then pulled back to engage        and remove the thrombus from the blood vessel. This is similar        to the disclosed structure in Published US Application        2004/0138692.    -   3) Another system, known in the trade as a “lasso” is basically        a simple catheter with a wire attached to its end. The wire        makes a loop and enters back into the catheter (e.g., a large        0.018 F microcatheter). The operator changes the aspect of the        loop by pulling on the wire. This system was originally        conceived to catch foreign bodies.    -   4) The Catch system of Balt is a stent closed on one end forming        a basket that is deployed distal to the thrombus. The operator        then pulls the system and retrieves the thrombus. This is        similar to the structure in FIG. 7 of U.S. Pat. No. 6,805,684.        The above systems may have various practical and cost        disadvantages. Although several of the commercial systems are        designed to penetrate clot, this may in fact be impossible if        the clot is made up of firm fibrin. The device may therefore not        penetrate the clot but instead will slide over the thrombus. The        process of engagement and retraction of a thrombus may also        fractionate the clot, producing distal embolization. Currently        available systems can also be difficult to guide or deploy at        the site of the thrombus, or may be traumatic to the artery, and        some systems are quite expensive. In addition, all these systems        are bulky and cannot be safely and effectively used in small        caliber blood vessels.

SUMMARY OF THE INVENTION

A device capable of isolating, capturing, and facilitating the removalof a thrombus in blood vessels (or stones in biliary or urinary ducts,or foreign bodies) uses a soft coil mesh with the aid of a pull wire toengage the surface of a thrombus, and remove the captured thrombus. Themechanical thrombectomy device is positioned by MRI or angiographyguided percutaneous transluminal catheter delivery within the lumen ofthe blood vessel directly adjacent to the thrombus. The soft coil meshis formed by an elongated microcoil element that forms the helicalelements of a macrocoil element having an adjustable stiffness whichprovides reliable dynamic compliance matching with the viscoelasticproperties of the thrombus undergoing removal. The microcoil elementsfurther provide a relatively elastic effect to the helical elementforming the macrocoil that allows for control of gripping forces on thethrombus while reducing non-rigid circumferential contact of the devicewith vessel endoluminal surfaces. The use of multiple coil meshelements, delivered through a single lumen or multiple lumen catheters,preferably with separate control of at least one end of each coil,provides a firm grasp on a distal side of a thrombus, facilitatingnon-disruptive or minimally disruptive removal of the thrombus uponwithdrawal of the device.

One aspect of the present invention is to provide a mechanicalthrombectomy system that can reliably and safely navigate tortuous bloodvessels to the site of an intracranial or extracranial thrombus.

A second aspect of the present invention is to provide a mechanicalthrombectomy device that can reliably and securely entrap a soft or hardthrombus without fragmenting the thrombus or damaging the intima of theblood vessel.

A third aspect of this invention is to provide a mechanical thrombectomydevice that is biocompatible, visible on both X-ray and MR imaging, andcompatible with standard medical catheters.

A further aspect of this invention is to provide a mechanicalthrombectomy device that can safely and completely remove thrombus ofany density from any blood vessel in the human body.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a macrocoil with microcoils therein.

FIG. 1A shows the microcoil/macrocoil structure of the soft coil capturedevice described herein.

FIG. 1B shows the macrocoil loops constrained in a microcatheter, with apull string attached to the distal tip of the macrocoil assembly whichextends out of the microcatheter, and a pusher wire attached to theproximal end of the macrocoil assembly.

FIG. 2 shows the deployment of two separate microcatheters, each with asingle macrocoil mesh element.

FIG. 2A shows the deployment of two separate microcatheters, each with aseparate macrocoil mesh element, each macrocoil mesh element havingseparate end controls extending from each microcatheter. The two meshelements are shown integrating on a distal side of a thrombus.

FIG. 2B shows the meshwork of the capture device in close contact withthe distal portion of a thrombus within an artery.

FIG. 3 shows the capture device in a more extensively associatedthrombus engaging position during the progression of the soft coildelivery.

FIG. 4A shows the capture device in a pre-capture position within anartery in a second mode of soft coil delivery, with the coil within afirst microcatheter and an extraction wire or extraction string providedfrom a second microcatheter.

FIG. 4B shows the capture device of FIG. 4A with the macrocoil/microcoilelement in a deployed position within an artery.

FIG. 5A shows the capture device in a format of providing two distinctmacrocoil/microcoil systems.

FIG. 5B shows the capture device in a format of providing two distinctmacrocoil/microcoil systems with separate extraction strings or separateretraction strings.

FIG. 6 shows a pneumatic delivery microcatheter delivery system withconstrained coils within the catheter.

FIG. 7 shows a dual lumen catheter system deploying two macrocoil meshelements, each with separate end controls of a mesh wire, which haveentwined beyond a thrombus.

FIG. 7A shows a series of steps in which a dual lumen catheter isdeploying two macrocoil mesh assemblies, each with separate end controlsof the mesh wire in each lumen. The macrocoils have entwined andprogressively encircle the thrombus as the microcatheter is withdrawn.

DETAILED DESCRIPTION OF THE INVENTION

The following description should be read with reference to the drawingswherein like reference numerals indicate like elements throughout theseveral views. The detailed description and drawings illustrate examplenon-limiting specific embodiments of the generic claimed invention.

FIG. 1 shows a structural material 2 that can be used as a soft coilcapture element in the practice of the technology described herein. Thematerial 2 has microcoils or microloops forming a continuing chain 6 ofmicrocoils that form the macrocoil or macrohelix 10. The term‘microcoil’ as used herein should not be confused with the RF or MRIresponsive coils or microcoils that are used in the medical imaging art.The microcoils of the present invention are small coils compared to themacrocoils 10 which are large coils. The microcoils are made from thestructural material (such as metal, polymeric or composite filament orwire) that forms the filaments, threads, fibers, or the like that areused to provide the microcoils that build into the macrocoils. Thebenefits of this material and the structure in which they perform willbecome apparent from the discussion herein.

The microcoils add a significant degree of dynamic compliance, effectiveelasticity, structural support and cushioning ability to the macrocoils.The microcoils elongate to give radial and circumferential elasticity tothe material 2, without providing hard and large abrasive surfaces thatmight damage adjacent endoluminal surfaces of the blood vesselsundergoing therapy, as would traditional coil or mesh structures. Uponremoval of the macrocoil from the catheter, the macrocoil expands andretains microcoils along a length of the macrocoil. Furthermore, forceis applied through the first wire on the distal end of the macrocoilthrombus engaging component adjacent to the catheter causes microcoilsto bend towards the proximal end of the macrocoil thrombus engagingcomponent and form loops.

FIG. 1B shows the attachment of the pull string 64 on the distal aspectof the macrocoil complex 10, and the attachment of the pusher(insertion) wire 67 on the proximal aspect of the macrocoil complex 10.The entire macrocoil complex 10 is constrained within the microcatheter66.

FIG. 2 shows the deployment of two separate microcatheters 66 a, eachwith a single macrocoil mesh element 2 passing between them. Themacrocoil mesh element 2 extends over a thrombus 72 within the maincatheter 50. The capture device 60 is shown, including the retractionstring 64.

FIG. 2A shows the soft coil material 10 within an artery 50. Themacrocoils 56 are shown with the entire length of the coil section 60 ofthe device being deployed in a slightly extended position beyond thethrombus 72. The pusher wires 67 a and 67 b stabilize the insertion ends68 a and 68 b of the soft coil material 10. The push wires 67 a and 67 btend to be thicker than the pull wires 64 a and 64 b as a matter ofcourse, but they may be designed to be of the same or similarthicknesses, and the pull wires may be thicker than the push wires 67 aand 67 b.

FIG. 2B shows the capture device 60 in an insertion position in initialcontact with the distal portion of a thrombus 72 within an artery 50. Apush wire 67 b is shown in an exaggerated position, extending beyond itsdelivery microcatheter 66 b. It is not necessary for the push(insertion) wire 67 b to itself exit the microcatheter 66 b, but onlythat it move so far forward as to assist the expulsion or deployment ofthe macrocoil material 10. The retraction wire or retraction string 64 bhas been shown in a position where it has pulled the material 10 intomore intimate contact with the thrombus 72, with the two microcatheters66 a and 66 b being themselves somewhat withdrawn from a positionpreviously distal to the thrombus 72.

FIG. 3 shows a first mode of delivery of the system wherein themicrocatheters 66 a and 66 b have been pulled past the thrombus 72 andthen retracted, and the push wires 67 a and 67 b has been slightlyextended beyond the microcatheters 66 a and 66 b (for illustrative andnot essential purposes). The pulling wire 64 b and the push wire 67 bare sufficiently close together so that the entire length of theextended coil 60 is restrained, but the extended and somewhat retractedcoil 60 encircles the major mass of the thrombus 72. The end of thepulling wires 64 a and 64 b have been retracted to pull the soft coilmaterial 10 into a tangled engagement with the thrombus, engaging thethrombus 72 so that withdrawal of the microcatheter and the four wires64 a, 64 b, 67 a, and 67 b will withdraw the thrombus 72 while enmeshedin the soft coil material. The entire enmeshing length 60 of the softcoil securely entrains the thrombus 72, and the soft coil material 10assists in reducing breakage of the thrombus 72 and damage to thevascular walls.

FIG. 4A shows the system 100 delivered in a second delivery mode, withthe microcatheters 106 a and 106 b passing the thrombus 72 mass. Thereis no push wire in this construction. Rather, there is a pull wire 112deployed from microcatheter 106 a so that the pull wire 112 ispositioned in front of the restrained soft coil material 114 even whileit is relatively in front of the thrombus 72. The insertionmicrocatheter has positioned an insertion or support element 110 whichhas been extended from the microcatheter 106 a to deploy the soft coilmaterial support element 114.

FIG. 4B shows that the pulling wire 112 has been extended (or retracted)slightly, causing the soft coil material 120 to deploy beyond thethrombus 72 and not yet enmesh the thrombus 72 within the soft coilmaterial 120. By withdrawing the microcatheters 106 a and/or 106 b, andthe two wires 116 and 110, the thrombus 72 can be first secured by themesh 120 and then withdrawn from the vessel 50 with minimal damage tothe vessel 50 and reduced breakage in the thrombus 72. The nature of themixture of the microcoils and macrocoils causes a constriction of thematerial around the thrombus, without segmenting (cutting) the thrombuseasily, and without providing a cage surface that is as potentiallydamaging to arterial walls as are other structures used for thrombusretrieval and capture.

The system is made of a 3D soft coil such that when the system getsdeployed, it has the tendency to form a three dimensional mesh, withloops of macrocoils extending across the inner lumen of the blood vesselto assure that loops will be able to engage a thrombus when the loopsare retracted. The ends of the coils may be attached on either itsproximal end to a pusher wire and to its distal end to a very fine pullwire or visa versa. The entire system may be in a very thin format(although the size may vary depending upon the need for fit withinparticular arterial passages), and can fit into a 0.010 inch innerdiameter microcatheter or smaller. Both the pusher wire attached to themacrocoils and the pull wire exit at the proximal end of themicrocatheter and can be manipulated by the operator. First themicrocatheter is positioned past the thrombus with the help of amicroguidewire, preferably between the thrombus and the inner wall ofthe blood vessel. Once the distal end of the microcatheter lies beyondthe thrombus (usually while it is in a distended state, fairly elongateand narrow), the microguidewire is exchanged for the thrombus retrievalsystem. The thrombus retrieval system is activated and deployed so thata significant portion of the entire length of coil (e.g., ⅕, ¼ orone-third of the coil) is positioned distal to the thrombus. A remainingsignificant portion of the coil (using, by way of non-limiting examplesof amounts, with one-third distal to or past the thrombus), such as atleast ⅕, at least ¼ or one-third or more of the coil length is wrappedaround or co-distant with the thrombus and ¼, ⅕ or one third or more isplaced proximal to the thrombus. Once the coil is deployed with asignificant portion at least at the distal end of the thrombus and moredesirably a significant portion past the distal end of the thrombus, theoperator pulls the thin distal pull wire, so that the mesh of coil loopsthat has formed around the thrombus or expanded beyond the thrombusretracts on itself and grabs securely the thrombus. The thrombus now canbe pulled out of the artery by pulling the microcatheter, the pusherwire and the thin distal wire at the same time out of the artery.

Other advantages of the system (in addition to what has been describedalready) are its very small size so it can retrieve thrombus from verysmall arteries, its capacity to pull out the thrombus in one piece, andits softness, allowing manipulation without trauma to the vessel wall.Larger versions have the advantage of retrieving a very large thrombusin one piece. This system may be used in any vessel of the body for theretrieval of thrombus or other material like foreign bodies.

The distal end of the soft coil material (where the pulling wire isattached) may be limited in its ability to extend away from the proximalend of the soft coil material (where the push wire is attached) by usingan internal connector, such as a thread, that attaches to both ends ofthe soft coil, and provides a physical limit to how far the coil may bedistended.

Whatever the consistency of the clot, i.e., soft or hard, once themicrocatheter has passed the clot, the distal mesh of coils whendeployed will form a tight cap that should bring back at least a largepart of the thrombus. The loops of the coil that surround the thrombus,producing a cocoon, will prevent the loss of parts of the thrombus if itbreaks into pieces. The tendency of the system to break soft thrombuswill depend on characteristics such as the soft coil material thickness,the microcoil thickness, the macrocoil thickness, density of themacrocoil, the 3D configuration of the macrocoils and the loop diameterof the coil. Even in the worst case envisioned, one could only deploy adistal and a proximal mesh or use a flow reversing system such as thatin the MERCI system.

The pull wire functions to pull the distal tip of the macrocoil tofacilitate the formation of a knot. If two macrocoils are used, a pullwire attached to each facilitates the formation of an even better knot.These knots are important to prevent the slippage of the macrocoils fromthe distal aspect of the thrombus during the removal process. After themacrocoils have been wound around the midportion and proximal aspects ofthe thrombus, the pull string is used to tighten the entire meshnetwork.

For a number of reasons, it may be desirable to capture and/or removeclots from the vasculature. The blood vessel can be essentially anyvessel or even a duct of the urinary or biliary tracts. The device mayinclude two or more longitudinal wires, for example a guidewire, a pushwire and a pull wire, as well as other functional wires (e.g.,conductive wires for other features provided with the device, such as aresistive wire to enable heating of the coils, if conductive/resistive.The basket member or region of soft coils is attached to or otherwisecoupled with the wires. In general, the device (wires and soft coilmaterial) can be advanced through the vasculature to a suitablelocation, for example past or adjacent to a clot, and expanded (whenpast or adjacent to the clot), so that the clot may be captured in thesoft coils, upon operator action, and the captured clot can be removedfrom the vasculature.

The device may be configured to shift between a first generallycollapsed configuration and a second generally expanded configuration,especially by the elastic memory of the coil material, and the guidanceimposed by the at least two wires. In at least some embodiments,shifting between these configurations includes the longitudinal movementof one or both of the wires relative to one another. Movement of theWires may occur in either the proximal or distal direction and, in thecase of both wires moving, may be in the same or opposite directions.Shifting may also result in one or both of the wires moving somewhatlaterally (especially with distally controlled wires on the coilmaterial (e.g., with materials that bend when heated, or the like, and aheating element attached thereto) so that the wires become closer ormove apart from one another.

Shifting between the collapsed and expanded configurations may occur ina number of differing manners. For example, the device or portionsthereof may be made of a shape-memory material (such as nickel-titaniumalloy or oriented coils) that can assume a pre-defined shape whenunconstrained or when subjected to particular thermal conditions.According to this embodiment, the device can be manufactured to be“self-expanding” (when the longitudinal distension and restraint by thewires is removed) so that it can be delivered in a collapsedconfiguration, then shift to the expanded configuration when aconstraint is removed (e.g., the distal ends of the two wires broughtcloser together) or when the device is subject to the natural thermalconditions within the blood vessel. Alternatively, shifting may occur bymechanically moving one or both of wires. Moving the wires may occur ina number of different ways such as by moving one or other of the wiresattached to the distal or proximal end of the coil material on thedevice.

As described above, all or portions of the device (including but notlimited to the coil materials and the wires) may be manufactured frompolymeric, metallic, natural (e.g., gut wires), synthetic, or compositematerials. Preferred materials tend to be polymeric, metallic, compositeor mixtures or combinations of these materials. A conventional medicalstructural material such as nickel titanium alloy may be employed.However, any suitable material may be used including metals, metalalloys, polymers, etc. Some examples of suitable metals and metal alloysinclude stainless steel, such as 304V, 304L, and 316L stainless steel;linear-elastic or super-elastic nitinol or other nickel-titanium alloys,nickel-chromium alloy, nickel-chromium-iron alloy, cobalt alloy,tungsten or tungsten alloys, MP35-N (having a composition of about 35%Ni, 35% Co, 20% Cr, 9.75% Mo, a maximum 1% Fe, a maximum 1% Ti, amaximum 0.25% C, a maximum 0.15% Mn, and a maximum 0.15% Si), hastelloy,monel 400, inconel 825, or the like; or other suitable material.

Some examples of suitable polymers may include polytetrafluoroethylene(PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylenepropylene (FEP), polyoxymethylene (POM), polybutylene terephthalate(PBT), polyether block ester, polyurethane, polypropylene (PP),polyvinylchloride (PVC), polyether-ester (for example a polyether-esterelastomer such as ARNITEL® available from DSM Engineering Plastics),polyester (for example a polyester elastomer such as HYTREL® availablefrom DuPont), polyamide (for example, DURETHAN® available from Bayer orCRISTAMID® available from Elf Atochem), elastomeric polyamides, blockpolyamide/ethers, polyether block amide (PEBA, for example availableunder the trade name PEBAX®), silicones, polyethylene (PE), Marlexhigh-density polyethylene, Marlex low-density polyethylene, linear lowdensity polyethylene (for example REXELL®), polyethylene terephthalate(PET), polyetheretherketone (PEEK), polyimide (PI), polyetherimide(PEI), polyphenylene sulfide (PPS), polyphenylene oxide (PPO),polysulfone, nylon, perfluoro(propyl vinyl ether) (PFA), other suitablematerials, or mixtures, combinations, copolymers thereof, polymer/metalcomposites, and the like. In some embodiments, portions of or all of thedevice can be blended with a liquid crystal polymer (LCP). For example,the mixture can contain up to about 5% LCP.

In some embodiments, a coating, for example a lubricious, a hydrophilic,a protective, or other type of coating may be applied over portions orthe entire device. Hydrophobic coatings such as fluoropolymers provide adry lubricity which improves device exchanges. Lubricious coatingsimprove steerability and improve lesion crossing capability. Suitablelubricious polymers are well known in the art and may include siliconeand the like, hydrophilic polymers such as polyarylene oxides,polyvinylpyrolidones, polyvinylalcohols, hydroxy alkyl cellulosics,algins, saccharides, caprolactones, and the like, and mixtures andcombinations thereof. Hydrophilic polymers may be blended amongthemselves or with formulated amounts of water insoluble compounds(including some polymers) to yield coatings with suitable lubricity,bonding, and solubility. Some other examples of such coatings andmaterials and methods used to create such coatings can be found in U.S.Pat. Nos. 6,139,510 and 5,772,609, which are incorporated herein byreference. In some embodiments, the sheath or coating may be appliedover basket region. This may provide extra surface area to contain clotsthat might be captured therein.

The sheath or polymeric layer coating may be formed, for example, bycoating, electrophoresis, by extrusion, co-extrusion, interrupted layerco-extrusion (ILC), or fusing several segments end-to-end. The layer mayhave a uniform stiffness or a gradual reduction in stiffness from theproximal end to the distal end thereof. The gradual reduction instiffness may be continuous as by ILC or may be stepped as by fusingtogether separate extruded tubular segments. The outer layer may beimpregnated with a radiopaque filler material to facilitate radiographicvisualization. Those skilled in the art will recognize that thesematerials can vary widely without deviating from the scope of thepresent invention.

The device, or portions thereof, may also be coated, plated, wrapped orsurrounded by, doped with, or otherwise include a radiopaque material.For example, the wires or coils may be made from a radiopaque materialor may include a radiopaque marker member or coil coupled thereto.Radiopaque materials are understood to be materials capable of producinga relatively bright image on a fluoroscopy screen or another imagingtechnique during a medical procedure. This relatively bright image aidsthe user of the device in determining its location. Some examples ofradiopaque materials can include, but are not limited to, gold,platinum, palladium, tantalum, tungsten alloy, plastic material loadedwith radiopaque filler, and the like.

An important practical concern in thrombectomy procedures is theaccuracy of the navigational process used to direct the endovascularplacement of a thrombectomy device relative to the location of athrombus. Magnetic resonance imaging can play an important role inlocalizing and characterizing the thrombus and in optimizing thepositioning of the thrombectomy device. High-speed, high-resolution MRimaging can now be combined with conventional X-ray fluoroscopy anddigital subtraction angiography (DSA) capability in a single hybridimaging unit. New generations of MR scanners provide frequently updatedimages of the anatomical structures of interest. This real-time imagingcapability makes it possible to use high-speed MR imaging to direct themovement of catheters and other components of the thrombectomy system tospecific endovascular locations, and thereafter observe the effects ofspecific interventional procedures.

MR imaging is also valuable in assessing the presence and size of anintracranial thrombus and in characterizing its age and composition. Agrowing body of evidence suggests that a combination of MR imaging andneurologic symptoms may in fact have prognostic predictive value inassessing patient outcome. During formation of a thrombus, the bloodcontains a mixture of oxyhemoglobin, deoxyhemoglobin and methemoglobinthat is usually equal to that of arterial blood. As the thrombus ages,however, the concentration of paramagnetic hemoglobin and methemoglobinwithin the clot also changes resulting in a characteristic appearance onMR images that reflects the age and stability of the clot. Observationof these MR imaging changes can be clinically useful in evaluating thepotential utility of various alternative interventions, such as, forexample, drug thrombolytic therapy versus mechanical thrombectomy.

The catheter tip on thrombectomy devices described in the prior art isdifficult to see on MRI because of inadequate contrast with respect tosurrounding tissues and structures. This makes accurate localizationdifficult and degrades the quality of the diagnostic informationobtained from the image. Thus, one objective of this invention is toprovide an MR-compatible and visible device that significantly improvesthe efficacy and safety of thrombus removal using MR guidance. Forexample, to enhance compatibility with MRI imaging systems, it may bedesirable to make portions of the device in a manner that would impart adegree of MRI compatibility. For example, the device, or portionsthereof, may be made of a material that does not substantially distortthe image and create substantial artifacts (artifacts are gaps in theimage). Certain ferromagnetic materials, for example, may not besuitable because they may create artifacts in an MRI image. The device,or portions thereof, may also be made from a material that the MRImachine can image. Some materials that exhibit these characteristicsinclude, for example, tungsten, Elgiloy, MP35N, nitinol, and the like,and others.

Any material that might be added to the structure of a pliable catheterto make it MR visible must not contribute significantly to the overallmagnetic susceptibility of the catheter, or imaging artifacts could beintroduced during the MR process. It is also important that thrombectomydevices used under MR guidance are MR-compatible in both static andtime-varying magnetic fields. Examples of such biocompatible andMR-compatible materials which could be used to practice the inventioninclude elastomeric hydrogel, nylon, teflon, polyamide, polyethylene,polypropylene, polysulfone, ceramics, cermets steatite, carbon fibercomposites, silicon nitride, and zirconia, plexiglass, andpoly-ether-ether-ketone.

Although the mechanical effects of the magnetic field on ferromagneticdevices present the greatest danger to patients through possibleunintended movement of the devices, tissue and device heating may alsoresult from radio-frequency power deposition in electrically conductivematerial located within the imaging volume. Consequently, all cables,wires, and devices positioned within the MR imaging system must be madeof materials that have properties that make them compatible with theiruse in human tissues during MR imaging procedures. Many materials withacceptable MR-compatibility, such as ceramics, composites andthermoplastic polymers, are electrical insulators and do not produceartifacts or safety hazards associated with applied electric fields.Some metallic materials, such as copper, brass, magnesium and aluminumare also generally MR-compatible, viz. large masses of these materialscan be accommodated within the imaging region without significant imagedegradation.

Guidewires for the catheter component of the thrombectomy system areusually made of radiopaque material so that their precise location canbe identified during a surgical procedure through fluoroscopic viewing.Exemplary of guidewires used under X-ray viewing is the guidewiredisclosed by LeVeen, U.S. Pat. No. 4,448,195, in which a radiopaque wirecan be identified on fluoroscopic images by metered bands placed atpredetermined locations. U.S. Pat. No. 4,922,924, awarded to Gambale etal. discloses a bifilar arrangement whereby radiopaque andradiotransparent filaments are wrapped on a mandril to form a bifilarcoil which provides radiopaque and radiotransparent areas on the guidewire. U.S. Pat. No. 5,375,596 to Twiss et al. discloses a method forlocating catheters and other tubular medical devices using an integratedsystem of wire transmitters and receivers.

Initial attempts to position and visualize endovascular devices such ascatheters in MR imaging were based on passive susceptibility artifactsproduced by the device when exposed to the magnetic field. Magneticsusceptibility is a quantitative measure of a material's tendency tointeract with and distort an applied magnetic field. U.S. Pat. No.4,827,931, to Longmore and U.S. Pat. Nos. 5,154,179 and 4,989,608 toRatner disclose the incorporation of paramagnetic material intoendovascular devices to make the devices visible under MR imaging. U.S.Pat. No. 5,211,166 to Sepponen similarly discloses the use of surfaceimpregnation of various “relaxants”, including paramagnetic materialsand nitrogen radicals, onto surgical instruments to enable their MRidentification. An improved method for passive MR visualization ofimplantable medical devices has been disclosed by Werne in U.S. Pat. No.5,744,958. In the method of the invention disclosed by Werne, an ultrathin coating of conductive material comprising 1-10% of the theoreticalskin depth of the material being imaged is applied. By using a coatingof 2,000-25,000 angstroms thickness, Werne has found that thesusceptibility artifact due to the metal is negligible due to the lowmaterial mass. At the same time, the eddy currents are limited due tothe ultra-thin conductor coating on the device.

However, these patents do not provide for artifact-free MR visibility inthe presence of rapidly alternating magnetic fields, such as would beproduced during echo-planar MR imaging pulse sequences used in real-timeMR guided thrombectomy procedures. Nor do these patents teach a methodfor monitoring with MR-visible catheters the outcomes of therapeuticinterventions, such as, for example, removal of a thrombus from theintracranial circulation followed by therapeutic drug delivery intobrain tissues. Thus, there is a continuing need to develop anMR-compatible and visible thrombectomy device that does not obscuresurrounding anatomy, and thereby compromise the physician's ability toperform the intervention.

The control wire(s) used to practice the present invention may beproduced from any number of suitable materials having reasonablestrength in tension, e.g., stainless steels, carbon fibers, engineeringplastics, tungsten alloys, variously in the form of a multi-strand cableor single strand thread. Preferably, however, the wire may be made froma “so-called” super-elastic alloy. These alloys are characterized by anability to transform from an austenitic crystal structure to astress-induced martensitic (SIM) structure and to return elastically tothe austenitic crystal structure (and the original shape) when thestress is removed. A typical alloy is nitinol, a nickel-titanium alloy,which is commercially available and undergoes theaustenite-SIM-austenite transformation at a variety of temperatureranges. These materials are described, for instance in U.S. Pat. Nos.3,174,851 and 3,351,463. These alloys are especially suitable because oftheir capacity to elastically recover almost completely to the initialconfiguration once the stress is removed. Since this is so, the size ofthe actual wire may be made fairly small, e.g., as small as 0.005 inchesin diameter or smaller, and the resulting device is able to access verysmall regions of the body. The wire may also vary in diameter along itslength, for example have a larger diameter at the proximal end ascompared to the distal end or vice versa.

The wires can have a proximal section and a distal section. The proximalsection preferably has a uniform diameter of at least about 0.0001 inch,or about 0.005 to 0.025 inches, preferably 0.0010 to 0.018 inches.Commercially available wires with a material (wire) diameter of 0.008 mmand a loop diameter of 1 mm are available as microcoil materials.Optionally, the distal section that may extend beyond the catheter mayhave different (more or less) flexibility than the proximal section.Typically, both sections will extend from the distal and proximal endsof the catheter lumen. The wire may have a middle section having adiameter intermediate between the diameter of the two portions of thewire adjoining the middle section or the middle section may becontinuously tapered, may have a number of tapered sections or sectionsof differing diameters, or may be of a uniform diameter along its lengthand be tapered at or near the distal section. The entire wire may bebetween about 50 and 300 cm, typically between about 175 to 190 cm inlength. The wire may be wrapped to form a coil section or may beindependently attached to a coil.

The overall length of the pusher wire, pull wire, and soft coil mesh mayextend through a catheter and the wires and catheter inserted into thevasculature. The catheter and wires (with attached soft coil) may extendproximal or distal to the site of the clot or the catheter may bepositioned and the wires extend to the site from the catheter. Theconfigurable soft coil component of the device is positioned near thetarget thrombus site, and the wires position and control the positioningand attitude of the soft coil capture components.

FIG. 5A shows the capture device in a format of providing two distinctmacrocoil/microcoil systems 132 and 134, with individual insertionelements 142 and 144. Both macrocoil/microcoil systems 132 and 134 areshown separately deployed and not yet engaged with each other. In apreferred embodiment, each macrocoil/microcoil systems 132 and 134 wouldalso have a pull string or retraction wire (not shown) on the ends ofthe macrocoil/microcoil systems 132 and 134 most distal from thethrombus 72.

FIG. 5B shows the capture device in a format of providing two distinctmacrocoil/microcoil systems 172 and 174 with separate extraction strings162 and 164 provided through a third catheter 160 or separate retractionstrings or pull strings 182 and 184, respectively.

FIG. 6 shows a pneumatic delivery microcatheter delivery system withconstrained coils within the catheter. FIG. 6 shows delivery system 202comprising a catheter 200 having the confined mass of themacrocoil/microcoil material 214 before deployment of the microcoilswithin the lumen of the catheter. Within the catheter 200 are twosealing elements 218 and 216 that form a pressurable zone 220 within thecatheter 200. The forward seal 216 is capable of being moved forwardwithin the catheter 200 by increased pressure within the zone 220. Amicrocatheter 224 is within the catheter 200 and a lumen 222 within themicrocatheter 224 carries fluid pressure and the retraction wire 230into the pressurable zone 220. When pressure in the zone 222 issufficient, the forward seal element 216 will press the compressedmacrocoil/microcoil mass 214 out of the catheter 200. The seal 216 willbe restrained by the retraction wire 230 that also is secured to one endof the contained mesh material 214.

FIG. 7A shows a two-lumen microcatheter 300 providing themacrocoil/microcoil mesh 302 with two separate control wires 304 and 306acting as the insertion wires. Retraction or pull wires are not shownbut are similar to those in FIGS. 1-3. The macrocoil/microcoil mesh 302is shown deployed beyond the thrombus 72.

FIG. 7B shows a series of steps a) b) c) and d) in which a dual lumencatheter 340 is deploying two microcoil/macrocoil mesh assemblies 350and 352 to form an engaged single macrocoil mesh 354 with separate endcontrol of the mesh wire in each lumen. The last three steps b) c) andd) represent a single mesh 354 delivered from the two adjacent lumens ina microcatheter 340, progressively encircling the thrombus 72. Twoseparate control ends 358 and 360 for controlling the composite mesh 354are shown.

Alternative processes and constructions could provide a soft coilcapture device (macrocoil/microcoil mesh) which may be of larger orsmaller dimensions than typical intravascular devices. With small coils,but particularly with larger coils, greater strength may be built intothe elastic memory of the material, and the length of the rememberedcoil distribution within the macrocoil element may be increased ordecreased. The coil material may be delivered through a catheter ormicrocatheter, with the elongation of the coils controlled by relativepositioning of the push (insertion) and pull (retraction) wires asexplained above. One end of the coil material may be secured to the push(insertion) wire, and the distal (leading end) of the coil material maybe secured to the distal end of the pull (retraction) wire. When in afully deployed state, without tension applied by the wires, a naturaldistribution (frequency) of the macrocoils may exist, but this is not atrue memory shape. It is only the random structure of the macrocoils andmicrocoils. Points of contact between the macrocoils and the pull wireare preferably not secured; rather, the macrocoils are able to slidefreely. If the contact points were secured, the frequency between thecoils would not be fixed after deployment, since the pull wire is ableto telescope or otherwise extend the distribution of the macrocoilswithin the mesh. The macrocoils, when in a region for deployment,without a restraining action through the connection at the distalconnecting point, may have a greater frequency (less spacing) betweenthe macrocoils. The microcoils and macrocoils may be manufactured anddesigned so as to provide natural dimensions when tension is releasedafter deployment to fit a range of dimensions in the vasculature. Theselection of the microcoil size, microcoil spacing, wire thickness, wirematerial, macrocoil size, and macrocoil spacing are used to determinethe frequency, size and shape of the deployed structure.

Although the examples show specific dimensions and materials, theexamples and descriptions are not intended to be limiting to the scopeof practice and protection of the technology described. Rather, anyspecific statements or values are intended to be examples within thegeneric concepts of the inventions and the disclosure taught andprovided herein.

Experimentation with the Thrombus Removal System has been conducted inorder to remove both soft and very firm clot from the arterial lumens ofmultiple arteries (renal, subclavian, common and internal carotidarteries) in the pig model. Soft clot was only a few hours old. Hardclot was made by allowing a pig's blood to stand for four days. Thefirm, fibrin-containing portion separated from the plasma, and the hardclot embolized into the selected artery of a second pig.

Both complex three-dimensional and less complex two-dimensional platinumcoils were used in these experiments, including coil structures thatwere not designed for use in thrombectomy procedures, but rather beingthe commercially available types used to fill cerebral aneurysms. Thesecoils have a variable cross-sectional diameter and length, and areattached to a stainless steel pusher wire. A commercially availablemicrocatheter with an inner lumen of 0.018 inch was passed beyond thethrombus, particularly between the intima and the thrombus (non-occludedspace between the thrombus and the walls) in the case of a firmthrombus, with the aid of a commercially available 0.014 inchmicroguidewire. A thin nylon line (0.006 inch) was attached to thedistal end of a coil, and the coil/string complex gently passed into amicrocatheter, to a point distal to the thrombus. Alternatively, thecoil/string complex was preloaded into the microcatheter that was passedwithout the aid of a microguidewire past the distal end of the thrombus.The coils were pushed from the microcatheter, which was progressivelypulled back until it was proximal to the thrombus and clot extractionattempted, as previously described.

Soft clot tended to be removed easily from the arteries studied becausethe clot adhered to the meshwork of the coil and the pulling wire.However, initial experiments with single coils of different sizes,including both 3-D and 2-D coils, demonstrated the inability toconsistently and successfully extract the firm clot with this method,even when the coil had formed a mesh around the thrombus and the nylonstring was pulled as much as possible to tighten the mesh around theclot. Rather, the coil sometimes simply unraveled from around thethrombus, sliding back into the more proximal microcatheter. It wasapparent that in those failed circumstances the loops of the coil weresimply wrapping around the clot without becoming tightly engaged, andthat such a non-structured mesh was insufficient to overcome thecombination of forces keeping the thrombus in place, including frictionbetween the thrombus and the intima and blood flow pushing the embolusdistally. However, intertwining and/or overlapping of the loops alongthe distal aspect of the thrombus, as one would tie a shoelace, kept thedistal mesh in place without allowing the entire coil complex tounravel.

In subsequent experiments, two microcatheters were passed distal to thefirm clot, each positioned in the same manner as previously described.The distal end of a 3-D coil was pushed into the arterial lumen from thefirst microcatheter, then the distal end of a second coil, either a 2-Dor a 3-D configuration, was pushed forward from the secondmicrocatheter, allowing loops of the two coils to intertwine. By “twocoils” in this description, it is meant that there are two masses ofcoils, one each delivered from a microcatheter, although the termincludes two coil masses emanating from two lumens of a singlemicrocatheter, as opposed to requiring two completely distinctmicrocatheters. Further coils were extended to make a complex, randommesh, then the nylon strings were pulled so that a tight “cap” or “knot”was formed on the distal surface of the clot. The microcatheters werepartially withdrawn and as more coils were pushed from themicrocatheter, they passively encircled the middle portions of the clot.The process was continued, with more coils (at least a total of two andup to six coils would be used in a preferred range of mesh applications)placed proximal to the clot. The nylon strings was then pulled tightlyto form a tight meshwork encircling the entire clot so that little or nofragmentation would occur.

Using this technique, it was possible to successfully extract firm clotsfrom all arteries embolized without evidence of fragmentation onsubsequent post-extraction angiography. Coils having diameters equal toor slightly larger than that of the arterial lumen appeared to make thebest distal meshwork and, therefore, the most stable macrocoilconstructs. By then passively encircling the clot, there was no tendencyfor the distal “cap” to simply slide from the top over the side of theclot. Post-extraction angiography and post-mortem examination, includingmicroscopy, did not demonstrate any evidence of arterial injury. Thiswas the expected result, given the extensive experience of using thesesoft platinum coils within the vascular system without producingvascular dissection or vasospasm.

Another way of generally describing articles and methods according tothe practice of the technology originally disclosed herein includes amedical device for removing a thrombus from a blood vessel, comprising:a) two microcatheter lumens, each lumen containing: b) a macrocoilthrombus engaging component having a length with a proximal end and adistal end, the length of the macrocoil comprising microcoils that allowthe length of the macrocoil to be extendable; c) a first wire capable ofproviding force on the distal end of the macrocoil; d) a second wirecapable of providing force on the proximal end of the macrocoil. Thedevice may have at least two lumens on distinct microcatheters, and theat least two lumens may be attached to a single catheter. A method maybe practiced for using the device wherein for at least one macrocoilthrombus engaging coil, a microguidewire is passed through at least oneof the lumens to help place the microcatheter distal to the thrombus;the microguidewire is removed; a macrocoil pull-string system comprisingpush-pull capability is passed through the at least one of the lumens;the macrocoil pull-string system is passed distal to the clot; thepull-string system is used to form an at least partially enclosingdistal meshwork on the distal surface of the thrombus, passivelyencircling mesh around the clot; the pull string is pulled to tightenthe meshwork; the macrocoils may have internal structures includingloops and other random attachments to facilitate the formation of atight meshwork; and at least a portion of the device is progressivelywithdrawn so that the meshwork becomes more tightly engaged with theclot. The method of using the device may be practiced wherein the atleast one set of microcoils of at least one macrocoil exhibits aconformation memory of an amorphous shape with overlapping structureresisting complete elongation when ends of the at least one macrocoilare stressed. The conformation memory may form at least one structureselected from the group consisting of knots, loops, multiple crossovers,kinks and snags to reduce excessive slipping of macrocoils, whichslipping would allow liner extension of macrocoil material. The methodmay have the at least one structure assist in forming a networkcomprising the at least one macrocoil engaging a distal surface of thethrombus. The method may be practiced so that the at least one macrocoilencircles or conforms to the surface of the distal side of the thrombusas the at least one macrocoil is extended from the microcatheter. Themethod may use a pull-string to tighten the at least one macrocoilagainst the distal side of the thrombus.

A dual lumen catheter or two separate catheters may deploy a singlemacrocoil mesh with controls on both ends, or two separate meshes, eachwith one or two separate end controls of the macrocoil mesh in eachlumen. Examples of the end control elements are a pull wire or push pullwire attached to either end of the macrocoil mesh. A thrombus usuallyhas a potential space between the thrombus and the wall of the vessel,allowing the soft macrocoil mesh to passively slid between the surfaceof the thrombus and the vessel wall. It is to be noted that the deployedmacrocoil mesh has no clearly defined shape (such as a basket, box,pyramidal coil complex, or the like) so that the macrocoil mesh mayconform to any surface, such as that of the thrombus, as it passivelysurrounds that surface. Proximal ends of the controlling wires orstrings may be used to control the location, deployment, tension,withdrawal and other movement of the macrocoil mesh by appropriatelypushing, pulling, twisting, orienting, reorienting, positioning orotherwise moving those proximal ends. Passively encircling the clotreduces the chance of unwanted fragmentation of the thrombus andsubsequent embolization of the fragment to vital tissues.

Where there is the deployment of two separate microcatheters, each witha separate macrocoil mesh element, each macrocoil mesh element may haveseparate end controls extending from each microcatheter, respectfully.Two mesh elements may integrate into a mass on the distal side of athrombus. Push-pull guidance wire combinations are provided for therespective pairs of macrocoil elements.

In the use of a dual lumen catheter system deploying two macrocoilmeshes with separate end controls for each mesh coming out of each lumenof the microcatheter, the distal ends of the mesh, the end controls mayoperate as push-pull wires, guidance wires, orientation elements,positioning elements, current carrying conductors (as when heating themicrocoils in the macrocoil mesh) and the like. The end controls may bethe same or different in the construction of the device to assure theirability to perform the ultimately desired tasks. Both end controls aidin the formation of a knot or tight tangle of the distal ends of eachmacrocoil mesh over the distal aspect of the thrombus, in the passiveencirclement of the mid and proximal portions of the thrombus, and inthe tightening of the meshwork around the surface of the thrombus.

It is to be noted that the dashed lines for catheters shown behindthrombus in some of the illustrations are not intended to limit theimages to catheters passing through the thrombus, and in fact as clearlydescribed herein, the location of the catheters is preferably adjacentto a thrombus. In this regard, it is one of the many novel aspects ofthe present technology that may be practiced according to theseteachings that the catheters are intentionally passed adjacent to andnot through a thrombus. It is also novel to pass multiple cathetersadjacent to a thrombus in a single medical procedure according to thetechnology described herein

There are numerous considerations of materials and properties that canbe discussed herein to provide general and specific assistance to thedesign of instruments for various locations and procedures. Thecomposition of the microcoils forming the macrocoil mesh may be anymaterial that will retain its structural integrity during the expectedlength of an extended procedure, with safeguards built in foroverextended periods of the coils being within an environment that maydeteriorate or dissolve them. For example, if a standard procedure wereexpected to take 1-2 hours, it would be appropriate if the coils wouldremain intact in the operational environment for at least 24 hours andretain their physical properties. The microcoil material can be allowedto breakup or even dissolve after that time, in the event that there isa problem during the procedure, such as if a coil breaks or separatesfrom the mesh.

Typically, the microcoil material will have essentially unaffectedproperties during the operation. Useful materials may be metals, alloys,plastics (polymeric materials), composites, ceramics and the like. Theproperties of the microcoil material are intended to provide themacrocoil mesh with resilient properties through the extensibility ofthe microcoils and macrocoils, and not necessarily elasticity in thematerial of the wire forming the various coils. The material of the wiremay in fact be clearly inelastic within standards for metal wire,plastic wire, ceramic wire and composite wire, for example, having lessthan 20% or 10% elongation at breaking point for the wire.

Deployment of the at least one wire (with macrocoil mesh therein) may befrom a single lumen on a catheter, multiple lumens on a single catheter,single lumens on multiple catheters, multiple lumens on multiplecatheters, and 1, 2, 3, 4, 5 6 or more catheters or microcatheters maybe used in the process.

The multiple coils may remain separate and distinct when deployed, mayincidentally overlap, may intentionally overlap, may tangle with eachother, may grip each other or otherwise interact. For example, when thedistal ends of the macrocoils are extended from the microcatheter lumens(one microcatheter with two lumens or two separate microcatheters withone lumen each), they will overlap to produce a knot, tangle, or otherfirm connection. In addition, one or more of loops (the macrocoil loops)may engage each other to form a loose, incidental lock or slip resistantengagement between one or more macrocoils. Design may be built into themacrocoils, such as spikes (less preferred because of potential wallirritation), hooks and loops, posts, and hooks alone to produce atighter mesh network and to decrease the likelihood of coil loops beingextended to relatively ineffectual linearity when one end control isfirmly pulled in attempting to position the mesh against the surface ofa thrombus.

There are many other variants that may be provided in the practice ofthe present technology. Among the variations to be considered is the useof actual knot-tying techniques using multiple macrocoil/microcoilstructures according to the present descriptions.

In the knot-tying format, two distinct macrocoils are fed from a singlelumen, at least two separate lumens, or at least two adjacent lumens,such that a first macrocoil forms a loop with an opening large enoughfor a straight segment of a second macrocoil to pass through theopening, then passing at least one second macrocoil through the opening,and adjusting the local relative positions of the now at least twomacrocoils so that a knot-like arrangement of the coils occurs. Theinteraction and engagement of the individual macrocoils of the at leasttwo macrocoils also acts to provide a supporting structure andcapability to the system.

This feature is more than superficially beneficial. When prior artcapture systems are analyzed, they are found to be essentiallyone-size-fits-all, with only minimum variability in the size of thecapture device allowed because of the more defined structure of thecapture portion, as can be noted in Rosenbluth (U.S. Pat. No.6,511,492), where a variety of cage and net structures are provided.Especially with the cage structures, the likelihood of a thrombus beingdisrupted during insertion and retraction is very high, especially withthe more rigid elemental constructions in the pyramidal coil and cagestructures. The relatively fixed size of the capture portion means thatthe system will use a single size for a large thrombus or a smallthrombus. The potential for damage or inoperability varies among therange of size of the potential thrombus, and might require an attempt toprovide distinct capture systems with advanced knowledge (which may beerroneous) of the specific size and shape of the thrombus. The presenttechnology, because of the flexibility and conformability of themacrocoil/microcoil structure, can be used on an extremely widevariation in size of thrombi, and the coils will themselves conform tothe size of whatever thrombus is present. The pull strings aid inaltering the position of the distal tip of one or more macrocoils, sothat the formation of the knot is facilitated. The pull string alsotightens the mesh work distal to the thrombus. Finally, after macrocoilsare passively looped around the mid and proximal aspects of the clot,the pull string aids in tightening the entire construct to decrease thechance of clot fragmentation.

Additionally, as noted elsewhere, the conformability of the macrocoilsystem of the described technology offers the potential for reduceddisruption of a thrombus and the generation of floating clots that couldcause a stroke. Although there is never a guarantee of avoiding suchissues during medical procedures, at least the potential is there forreducing the likelihood of such potentially disastrous events.

Other variations in the materials, designs and processes may be apparentand obvious to those skilled in the art from the generic teaching andexamples provided herein.

What is claimed:
 1. A medical device for removing a thrombus from ablood vessel, comprising a single catheter containing: a macrocoilthrombus engaging component having a length with a proximal end and adistal end, the length of the macrocoil comprised of microcoils thatallow the length of the macrocoil to be extendable and flexible; a firstwire capable of providing force on an end of the macrocoil; within thecatheter are two sealing elements, a first forward-sealing element and asecond rearward-sealing element that form a pressurable zone within thecatheter; the first wire is a retraction wire for the firstforward-sealing element; wherein upon removal from the catheter by forceon at least the first forward-sealing element, the macrocoil expands andretains microcoils along a length of the macrocoil.
 2. The medicaldevice of claim 1 wherein when the first forward-sealing element and aportion of the microcoils are extending from, but adjacent to, thecatheter, the macrocoil is in a naturally expanded condition.
 3. Themedical device of claim 2 wherein the medical device is configured to bepresent within the blood vessel having a thrombus therein, and thedistal end of the macrocoil thrombus engaging component is configured toextend past the thrombus.